In the field of biomedical research studies involving the cloning of cells for the purpose of determining the response of human tumor cell colonies to chemotherapeutic drugs, the colonies of tumor cells are commonly grown in a medium and gel-like agarose placed in petri dishes. The cell colonies are exposed to different drugs in various concentrations, and usually, the cell colonies are manually counted by technicians viewing the colonies through a low-powered inverted microscope.
As an alternative to this manual counting procedure which is fatiguing, time consuming, prone to inaccuracies and expensive, an image analyzer has been developed by Bausch & Lomb and has been marketed under the trademark OMNICON. This machine or system automatically scans, selects and counts tumor colonies in the agarose culture within the petri dishes and uses optical and computer technology to obtain a faster and more accurate counting of the cell colonies. The machine has been used in basic research to study the effects of growth factors, carcinogens, promoters, growth inhibitory factors and differentiation inducers on single cells and on cell colonies.
In an effort to increase cloning efficiency and reduce perassay costs, a capillary cloning procedure has been developed and used as an alternative to the petri dish counting procedure. The cells are inserted into the capillary tubes and cell colonies are grown within the agarose culture. The cell colonies are counted manually by a person viewing the contents of each capillary tube through a microscope. Several years ago, a prototype automated data collection and analysis system was developed by Triton Biosciences Inc., a subsidiary of Shell Oil Company, for use with the capillary tube cloning technique. The prototype units were introduced under the trademark CELLSCAN and included an automated X-Y stage microscope, a rack for holding a set of capillary tubes each having a square cross-section, a DC-powered light source and a light detector and amplifier. All of these components were interfaced with a computer through a microprocessor. The light source was located directly above the object lens of the microscope on the vertical optical axis of the lens, and each capillary tube was moved longitudinally and horizontally through the optical axis for scanning the contents of each tube. A plate with a narrow slit was positioned between the downwardly directed light and the capillary tube under the light to restrict the illumination field. When a capillary tube was moved across the light directed through the slit, some data was collected with respect to the number and size of the cell colonies and the axial locations of the colonies within each capillary tube.
The square capillary tubes were selected to improve illumination of the cell colonies within the tubes since a conventional cylindrical capillary tube resulted in reflecting a high percentage of the light and poor illumination of the cell colonies. It was also determined that the use of the square capillary tubes and the illumination system used on the CELLSCAN unit resulted in a low signal-to-noise ratio from the optical detector. As a result, the accuracy and repeatability of the CELLSCAN system was not satisfactory, and further development of the system was discontinued in 1985 by Triton Biosciences Inc. In addition, since the square capillary tubes were made by fusing two L-shaped strips together, the tubes were expensive to manufacture, and the costs of the disposable tubes significantly increased the costs for each investigation.